Page:UK Traffic Signs Manual - Chapter 3 Regulatory Signs. 2008 (Second Impression 2008).pdf/167



NOTE 1: 85th percentile speed measurement is dealt with in TA 22 / 81 "Vehicle speed measurement on all-purpose roads" in Volume 5 of the Design Manual for Roads and Bridges (see para 1.3). The right hand column (over 60 mph) applies generally to all-purpose dual carriageway roads and, where appropriate, to motorways. It should be noted that other factors such as carriageway width and the complexity of the background against which the sign is placed may also affect sign size (see notes 2 and 3 below).

NOTE 2: The smaller bracketed sign sizes should be used only where special amenity considerations or physical constraints apply. It should be borne in mind that smaller signs are likely to be seen later, and do not become legible until drivers are closer to them, with less time to react.

NOTE 3: The larger bracketed sign sizes should be used where site conditions require increased conspicuity, such as on a wide road or where the accident record calls for greater emphasis. Conspicuity can also be increased by the use of yellow backing boards (see paras 1.31 to 1.33).

NOTE 4: The size of a sign and its corresponding supplementary plate should be taken from the same column. Where two sizes are shown for both the sign and the plate, corresponding sizes (smaller or larger) should be used. 165